Push button switch assembly and ferrule therefor



March 8, 1966 M. Y. TURNBULL PUSH BUTTON SWITCH ASSEMBLY AND FERRULE THEREFOR 2 Sheets-Sheet 1 Filed Nov. 5, 1962 INVENTOR.

711x44 BY 1 ATTOR N EY.

March 8, 1966 M. Y. TURNBULL 3,239,640

PUSH BUTTON SWITCH ASSEMBLY AND FERRULE THEREFOR 2 Sheets-Sheet 2 Filed Nov. 5, 1962 I 'ZFATTORNEY United States Patent 3,239,640 PUSH BUTTON SWITCH ASSEMBLY AND FERRULE THEREFOR Merlin Y. Turuhull, Brookfield, Wis., assignor to Square D Company, Park Ridge, Ill., a corporation of Michigan Filed Nov. 5, 1962, Ser. No. 235,207 4 Claims. (Cl. 2t)0168) This invention relates to a ferrule for peripherally enclosing the push button of push button switches, and particularly to a plastic ferrule which is arranged to be snapped into the push button opening in a cover or flush plate of a push button switch and engage the wall of the opening so as to secure itself to the plate and provide a peripheral guard for the push button.

For purposes of illustration, the ferrule is shown herein as mounted in a flush plate for push button switches, which plate also is the cover plate for a box in which the push button switch is contained. A push button switch generally is mounted behind a sheet metal plate with the push button extending through a suitable opening in the plate for access at the forward face of the plate. Some times the switch is mounted directly on the rear face of the plate. In other cases it is mounted in a receptacle of which the plate forms the cover.

Heretofore, such plates have been provided with meta ferrules which are secured in guarding relation to the periphery of the push button by spinning the margins of the ferrules into clamping engagement with the margins of the plate defining the opening. The push button extends through the ferrule. Generally, indicating plates bearing indicia are secured by rivets to the plates, respectively, adjacent the ferrule. In accordance with the present invention, a ferrule for the same general purpose of peripherally enclosing and guarding the push button is provided.

The ferrule of the present invention comprises generally an annular body of relatively rigid, but slightly deflectable, self-restoring plastic.

The ferrule is one which can be pressed axially into the push button opening of a cover or flush plate and when so inserted, is self-restoring and connects itself effectively to the plate in position for peripherally surrounding the push button. The ferrule preferably has a radially extending passage extended peripherally so as to receive radially of the ferrule an element which, when in operative position, secures the push button in a preselected axial position; for example, in depressed position. The element is arranged so that it can be locked in its operative position so as to prevent tampering with, or inadvertent operation of, the push button. In addition, the ferrule is one which, when connected to the cover plate or flush plate, holds in place an indicating plate bearing indicia which indicates the purpose of the switch.

Various other objects and advantages of the present invention will become apparent from the following description wherein reference is made to the drawings, in which:

FIG. 1 is a perspective view of a push button switch container with the present invention installed on the front cover plate thereof;

FIG. 2 is a fragmentary front elevation of the cover plate in which the opening for a push button is provided;

FIG. 3 is a front elevation of an indicating plate to be connected to the cover plate by the present ferrule;

FIG. 4 is an enlarged front elevation of the ferrule illustrated in FIG. 1;

FIG. 5 is a sectional view of the ferrule taken on the line 55 of FIG. 4;

FIG. 6 is an enlarged sectional View of the ferrule and part of the cover plate of FIG. 1 and is taken on the line 66 in FIG. 1;

ice

FIG. 7 is a view similar to FIG. 6 showing the ferrule prior to installation, but in position to be installed, in the position illustrated in FIG. 6;

FIG. 8 is a front elevation of a ferrule similar to that illustrated in FIG. 4, but showing a modification thereof;

FIG. 9 is an axial sectional view taken on the plane 9-9 in FIG. 8;

FIG. 10 is a view of the ferrule illustrated in FIG. 3, as viewed from line ill-10 of FIG. 8;

FIG. 11 is a view similar to FIG. 8 showing another modification of the ferrule; and

FIG. 12 is a sectional view taken on the line 12-12 of FIG. 11.

Referring to FIG. 1, the invention is shown as incorporated with a push button switch in a container indicated generally at 1 and having top and bottom walls 2, and a front cover plate .3 which also may serve as a flush plate customary for switches of this character. Within the container 1 is a push button switch, indicated at 4, which may be secured to the rear wall of the container, not shown. The cover plate 3 is secured to the container by screws 5. The switch has a conventional push button 6 which extends through a suitable opening 7 in the plate 3. Mounted in the opening so as to be in coaxial and surrounding relation to the push button 6 is the ferrule 10 of the present invention.

The ferrule 10 is preferably composed of one of the relatively rigid, but elastically deformable synthetic organic plastics, having high resistance to creep, or cold flow. It is accurately self-restoring quickly to its original shape, that is, it has a good memory. An example is Delrin marketed by E. I. du Pont de Nemours & Co., Inc. of Delaware, and is an acetal resin superpolyoxymethylene high-melting highly crystalline stable polymer with unique carbon to oxygen to carbon structure being a linear acetal which may be represented by the formula. (OCH Nylon may be used but is not as desirable.

The ferrule 10 is in the form of an annular body having an axial passage 11 therethrough which, when the ferrule is installed in the opening 9, is coaxial with the push button 6 and accommodates the push button with operating clearance between the peripherally adjacent walls of the button and passage 11.

In order that the ferrule can be readily installed in the passage opening 9, it is provided with an integral peripherally extending ledge means 12 which has a frustoconical portion 12a which tapers inwardly radially toward the adjacent end of the ferrule and a coaxial cylindrical pilot nose portion 12b of the same diameter as, and extending from, the smaller base of the frusto-conical por tion 12a to the adjacent end of the ferrule. The nose portion 12b is preferably of a diameter to fit the opening 7 with slight operating clearance thereby preventing tilting of the ferrule relative to the axis of the opening 7 and thus facilitating installation. The shoulder 13 faces toward the other end of the ferrule so as to be engageable with the rear of the plate 3. The ferrule has an integral second ledge means 14 which is coaxial with the shoulder 13 and preferably has a peripheral rim 15 of greater diameter than the outer diameter of the shoulder 13. The second ledge means has a free end 16 spaced from the shoulder 13 in a direction away from said one end toward the other end of the ferrule. The marginal portion of the free end 16 is thin in cross section relative to the wall thickness of the body of the ferrule so as to be more readily flexed, for purposes later to be described.

The shoulder 13 has a greater outer diameter than the bounding wall of the opening 9 so that the ledge 12 cannot pass entirely through the opening. However, the ledge shoulder is such that it can be contracted radially by placing the smaller end of the ferrule in the opening 9 in coaxial relation with the opening and pressing the ferrule axially toward the forward face of the plate 3. This contracts the ledge means 12 radially inwardly to a diameter adequately small to pass entirely through the opening 9. When the shoulder 13 passes the rear face of the plate, the shoulder becomes self-restoring to a diameter greater than that of the opening 9.

The distance between the shoulder 13 and the free end margin 16 in a direction axially of the ferrule is less than the thickness of the plate 3 to be received therebetween. As a result, upon insertion of the ferrule, to dispose the shoulder 13 past the rear face of the plate, the free margin 16 is deflected and stressed against the plate 3 and when the shoulder 13 is snapped behind the plate 3, the free end 16 is retained in resilient pressure engagement against the forward face of the plate 3 while the rear face of the plate 3 is engaged with the shoulder 13. This anchors the ferrule firmly in place.

In general, however, an indicating plate is desired adjacent the push button. For this purpose, a thin metal plate 20 is provided. The plate 20 has an annular portion with an opening 21 therethrough of adequate size to surround the push button, and a tab 22 on which are suitable indicia indicating the purpose of the particular push button. For installation, the plate 20 is disposed in face to face juxtaposition with the plate 3 with the openings 21 and 9 in axial alignment.

In the installed position of the ferrule, the shoulder 13 is positioned axially to engage the inner face of the plate while the free margin 16 bears against the forward face of the plate 20, thus yieldably holding the plates 3 and 20 in face to face juxtaposition and in stressed engagement with the ferrule. The two plates 3 and 20 thus are, in effect, a single plate or plate means insofar as concerns the fastening of the ferrule in place around the push button.

It is desirable to place the indicating tab 22 of the indicating plate in different positions circumferentially of the axis of the opening 9. For this purpose, complementary positioning means are provided on the plates 3 and .20. In the form illustrated, the positioning means comprise nibs on one of the plates adapted to cooperate with one or more tongues on the other. For illustrative purposes, nibs 25 are provided on the plate 3. These nibs are preferably arranged in pairs, the pairs being spaced 90 from each other about the periphery of the openings 9 so as to provide four positions. The plate 20 has a suitable complementary positioning means in the form of a tongue 26 with shoulders 27. The shoulders 27 are arranged to engage between two nibs of any one of the pairs, selectively, for holding the plate 20 in a preselected rotated position about the axis of the opening 9.

Preferably, the nibs 25 are arranged peripherally of the opening 9 so as to engage the peripheral wall of the opening 21 and thus position the plate 20 edgewise with its opening 21 coaxial with the opening 9.

Thus with the plate 2%) juxtaposed against the plate 3 with its opening 21 aligned with the opening 9, and with the tab 22 rotated to the desired position and held therein by the tongue 26, the ferrule is passed from the forward face of the plate 3 through the aligned openings so that the shoulder 13 snaps into engagement with the rear face of the plate 3 and the free margin 16 resiliently and engages the forward face of the indicating plate 20 under stress so that the ferrule clamps the plates firmly together.

As mentioned heretofore, it is desirable at times to lock the push button in an operative or inoperative position. In the form illustrated, means are provided for this purpose, these means being arranged to lock the push button in the depressed condition. This means comprises a suitable slide 30 supported in a bracket 31 which may be welded on the plate 3. The slide 30 is guided by a rivet 32 passing through an elongated slot 33 in the slide. In order that the inner end of the slide, indicated at 34, overlies the depressed push button when the slide is in its innermost position, a suitable radial passage 35 is provided in the ferrule. The passage 35 is elongated circumferential- 1y of the ferrule and generally is positioned axially of the openings so that the slide 30 may pass therethrough and overlie the depressed push button. For this purpose, it is arranged so that it is between the forward end of the ferrule and extends from the forward end toward the opposite and at least to the free margin 16.

The slide 31) has an upturned outer end 37 which, when the slide is in its innermost position radially of the openings, lies alongside an upturned ear 38 on the plate 3. The ear has an aperture 39 for receiving a padlock hasp which, when the slide 31 is moved inwardly sufficiently so that its inner end overlies and thus holds the push button depressed, engages the upturned end 37 and prevents movement of the slide outwardly to releasing position.

The ferrule is installed by first positioning it as indicated in FIG. 7 with its smaller end partly inserted into the opening 9 of the plate 3, the name plate being first juxtaposed on the plate 3 and held in alignment by the nibs 25. The ferrule is then pushed axially inwardly, or downwardly in FIG. 7, until the shoulder 13 passes the inner face of the plate 3 and is self-restored to its original diameter, thus engaging the rear face of the plate 3. The same operation stresses the thin free margin 16 against the outer face of the plate 20, the margin 16 flexing as indicated at 16a. Upon release of the ferrule, the shoulder 13 and margin 16 are in resilient stressed engagement with the opposite faces of the plate means, including the indicating plate and the flush plate or cover.

In some instances, it is desirable that the ledge means which engage the rear face of the flush plate be interrupted. For this purpose, as illustrated in FIGS. 8 through 10, ledge means such as indicated at 43 are provided, these ledge means being the same as the ledge means 12 heretofore described except that they are interrupted circumferentially of the ferrule. Preferably, each portion of the ledge means 43 extends for about one quadrant of the ferrule. The portions are symmetrically arranged with respect to the axis of the ferrule. A complementary ledge means 44, corresponding to the ledge means 14, may be continuous, as heretofore described. In all other respects, the ferrule of FIGS. 8 through 10 is the same as that above described.

This ferrule has distinct advantage in that in molding, the ledge means 43 can readily be disengaged from the mold by rotating the ferrule about its axis before axially withdrawing it.

In some instances, it is desirable to operate the push button by a so-called mushroom head. For this purpose, a structure such as illustrated in FIGS. 11 and 12 is employed. It comprises a plate 49, similar to the plate 3, which carries a ferrule 50, the same as the ferrule 43 of FIGS. 8 through 10. This ferrule has a first ledge means 51 with a circumferentially interrupted shoulder 52, and a peripheral margin 53. The margin of the plate 49 defining the openings therein, is received between the shoulder 52 and peripheral margin 53 and is clamped firmly therebetween. An indicating plate, such as the one heretofore described, may be provided if desired. The first ledge means slopes inwardly toward the axis in a direction away from the shoulder and at its inner end has a cylindrical guiding or pilot nose 54.

The ferrule 50 has a shoulder 55 which, in the installed position of the ferrule, is spaced outwardly from the plate 49. The shoulder 55 is annular and has at its inner end a sleeve portion 56 which snugly receives a stem 57 for axial reciprocation. The stem 57 is threaded, as indicated at 58, for threaded engagement with an internal bore of a mushroom head 59. At its inner end, the stem 57 has an annular rirn 60 which, at its outer margin, underlies the shoulder 55 and is of greater diameter than the sleeve 56. A push button 61 is provided and has a button engaging head 62 extending inwardly from the annular rim 60 and engages the outer end of the push button 61. Thus the stem 57 forms, in effect, a continuation of the push button 61.

The stem is urged outwardly by the push button 61. The inner button engaging head 62 is hexagonal and c0- axial with the stern and extends inwardly axially of the stem a distance such that when it is in engagement with the outer end of the push button 61, and holding it in depressed position, the rim 60 is spaced axially from the push button. This spacing is sufficient to that a locking slide 63, similar to the slide 30, may be moved between the rim 60 and push button 61 for locking the push button in depressed position. If desired, a spring 64 may be interposed between the rim 60 and shoulder 55 to hold the head 62 firmly against the button 61.

It is apparent from the foregoing description that each of the ferrules illustrated may readily be installed with a flush plate or cover and when so installed would enclose the push button effectively. Further, the installation is relatively simple and yet when installed the push button is very rigid and held rigidly in position on the cover or the flush plate. Furthermore, when desired, it can be made to hold the indicia plate firmly in place. The ferrule shown may be removed, if need be-for instance, for changing the indicia plate, simply by pressing it axially from the rear face of the plate toward the front face.

Having thus described my invention, I claim:

1. A ferrule for peripherally enclosing the push button of a push button switch and comprising an annular body of relatively rigid, slightly defiectable, self-restoring, synthetic plastic, said body having a central axial passage adapted to accommodate a push button in coaxial relation with operating clearance, and having a peripheral wall surrounding the passage, said peripheral wall having a first peripherally extending external ledge means spaced from the ends of the body and facing one end, and having a second peripherally extending external ledge means spaced, toward said one end, from the first ledge means axially of the body and facing toward the other end of the body, and said second ledge means having a rim disposed outwardly, transversely of the ferrule, from the first ledge means, the rim having a free marginal portion which is thin in cross section relative to the wall thickness of the body and extends toward the first ledge means, said first ledge means being interrupted peripherally of the body, the ends of the interrupted portions being of equal width peripherally of the body, the peripheral spaces between the interruptions being of equal width peripherally of the body, and the width of each peripheral space being equal to the peripheral width of each interrupting portion.

2. In a push button operated switch structure, plate means having an opening therethrough for a push button,

an annular ferrule of relatively rigid, slightly defiectable but self-restoring material having an axial passage and a peripheral wall surrounding the passage, said ferrule being accommodated in the opening with its axial passage coaxial with the opening, said peripheral wall having a first peripherally extending external ledge means spaced from the ends of the ferrule and facing one end thereof and having a second peripherally extending external ledge means spaced axially of the ferrule toward said one end from the first ledge means and facing toward the other end of the ferrule, said first and second ledge means being in stressed engagement with opposite faces of the plate means, respectively, said peripheral wall having a radial passage extending therethrough and elongated peripher ally of the ferrule, said radial passage being disposed, endwise of the ferrule adjacent that wall of the plate means which is engaged by the second ledge means so as to be accessible radially of the ferrule at said face of the plate means while the ferrule is supported by the plate means disposed between the first and second ledge means, said plate means comprising a first plate, a second plate juxtaposed against the forward face of the first plate in face to face relation and engaged at its forward face by said second ledge means, said openings being aligned openings in the plates, respectively, and circumferentially spaced pairs of nibs on the juxtaposed face of one plate and a tongue portion on the other plate engageable, selectively, between the nibs of the pairs, respectively.

3. In a push button operated switch structure, a plate having an opening therethrough for a push button, a ferrule of stiff, defiectable, self-restoring, molded material accommodated in the opening, said ferrule having inner and outer ends and a central axial passage, a peripheral wall surrounding the passage, first external peripheral ledge means on the ferrule spaced from said outer end and of slightly larger diameter than the plate opening and elastically compressible to pass, inner end foremost, through the plate opening, said ferrule having a second external peripheral ledge means spaced from said outer end a lesser distance than the first ledge means, said two ledge means being in concurrent engagement with the opposite faces, respectively, of the plate about the plate opening, a first push button having one portion accommodated in the ferrule passage for movement axially inwardly and outwardly thereof, said portion having an operating head accessible for operation at the other end of the ferrule, complementary movement limiting means on said portion and in the ferrule, between the ends of the ferrule passage, and engagable when said one portion moves outwardly axially of the ferrule passage, to constrain it from movement outwardly beyond a predetermined extended position, a second push button disposed inwardly, axially of the ferrule passage, from said first push button and movable axially of the ferrule passage to extended and retracted positions and disconnected from the first push button, means on the inner end of said one portion and engaging said second push button for holding the push button in axially spaced relation to e ach other, said ferrule having a lateral passage through it's peripheral wall, a locking member movably mounted on said plate and having a locking portion received through the lateral passage and movable to locking position in the central passage, and said lateral passage being positioned axially of the ferrule so that, when said second push button is in a predetermined retracted position and the locking portion is in locking position, the locking portion is disposed between said push buttons for constraining said second push button from movement from its said predetermined retracted position toward its extended position.

4. In a push button operated switch structure, plate means having an opening therethrough for a push button, an annular ferrule of relative rigid, slightly defiectable but self-restoring material having an axial passage and a peripheral wall surrounding the passage, said ferrule being accommodated in the opening with its axial passage coaxial with the opening, said peripheral wall having a first peripherally extending external ledge means spaced from the ends of the ferrule and facing one end thereof and having a second peripherally extending external ledge means spaced axially of the ferrule toward said one end from the first ledge means and facing toward the other end of the ferrule, said first and second ledge means being in stressed engagement with opposite faces of the plate means, respectively, said peripheral wall having a radial passage extending therethrough and elongated peripherally of the ferrule, said radial passage being disposed, endwise of the ferrule, adjacent that wall of the plate means which is engaged by the second ledge means so as to be accessible radially of the ferrule at said face of the plate means while the ferrule is supported by the plate means disposed between the first and second ledge means, said plate means comprising a first plate, a second plate juxtaposed against the forward face of the first plate in face to face relation and engaged at its forward face by said second ledge means, said openings being aligned openings in the plates, nibs on one plate spaced from each other peripherally of its opening and engaging the peripheral edge of the opening in the other plate for holding the plates with their openings in alignment, and

a tongue on the other plate projecting inwardly of the opening of its associated plate, and engaging between adjacent nibs, selectively, depending on the relatively 5 rotating position of the plates about an axis through the openings and normal to the plates.

References Cited by the Examiner UNITED STATES PATENTS Robbins 70 1s1 X 15 8 2,889,089 6/1959 Herrick et a1. 2S5-423 3,001,007 9/1961 Klurnpp 174-153 3,096,026 7/1963 Bruce et al. 174153 FOREIGN PATENTS 620,961 4/ 1949 Great Britain.

803,276 10/1958 Great Britain.

352,724 4/ 1961 Switzerland.

OTHER REFERENCES Breuer: (German application) 1,049,465, Jan. 29, 1959.

KATHLEEN H. CLAFFY, Primary Examiner.

BERNARD A. GILHEANY, Examiner. 

1. A FERRULE FOR PERIPHERALLY ENCLOSING THE PUSH BOTTON OF A PUSH BOTTOM SWITCH AND COMPRISING AN ANNULAR BODY OF RELATIVELY RIGID, SLIGHTLY DEFLECTABLE, SELF-RESTORING, SYNTHETIC PLASTIC, SAID BODY HAVING A CENTRAL AXIAL PASSAGE ADAPTED TO ACCOMODATE A PUSH BOTTOM IN COAXIAL RELATION WITH OPERATING CLEARANCE, AND HAVING A PERIPHERAL WALL SURROUNDING THE PASSAGE, SAID PERIPHERAL WALL HAVING A FIRST PERIPHERALLY EXTENDING EXTERNAL LEDGE MEANS SPACED FROM THE ENDS OF THE BODY AND FACING ONE END, AND HAVING A SECOND PERIPHERALLY EXTENDING EXTERNAL LEDGE MEANS SPACED, TOWARD SAID ONE END, FROM THE FIRST LEDGE MEANS AXIALLY OF THE BODY AND FACING TOWARD THE OTHER END OF THE BODY, AND SAID SECOND LEDGE MEANS HAVING A RIM DISPOSED OUTWARDLY, TRANSVERSELY OF THE FERRULE, FROM THE FIRST LEDGE MEANS, THE RIM HAVING A FREE MARGINAL PORTION WHICH IS THIN IN CROSS SECTION RELATIVE TO THE WALL THICKNESS OF THE BODY AND EXTENDS TOWARD THE FIRST LEDGE MEANS, SAID FIRST LEDGE MEANS BEING INTERRUPTED PERIPHERALLY OF THE BODY, THE ENDS OF THE INTERRUPTED PORTIONS BEING OF EQUAL WIDTH PERIPHERALLY OF THE BODY, THE PERIPHERAL SPACES BETWEEN THE INTERRUPTIONS BEING OF EQUAL WIDTH PERIPHERALLY OF THE BODY, AND THE WIDTH OF EACH PERIPHERAL SPACE BEING EQUAL TO THE PERIPHERAL WIDTH OF EACH INTERRUPTION PORTION. 